U.S. patent number 7,043,273 [Application Number 10/045,024] was granted by the patent office on 2006-05-09 for diversity branch delay alignment in radio base station.
This patent grant is currently assigned to Telefonaktiebolaget LM Ericsson (publ). Invention is credited to Ning He, Thomas Leif Ostman, Lawrence Sarresh.
United States Patent |
7,043,273 |
Sarresh , et al. |
May 9, 2006 |
Diversity branch delay alignment in radio base station
Abstract
A base station (28) included in a radio access network of a
telecommunications system has two diversity antennas (44A, 44B) for
a cell/carrier utilized in a sector served by the base station
which are respectively involved in transmission of two branches of
a radio link signal of the cell/carrier between the base station
and a user equipment unit (30). Two branches of signal processing
hardware respectively process the two branches of the radio link
signal to yield two respective processed branches of the radio link
signal. A rake receiver (62, 262) measures the delay difference
between the two processed branches of the radio link signal, and
uses the measured delay difference for various purposes. For
example, some embodiments of the invention use the delay difference
between the two branches as measured by the rake receiver to
compensate for a delay difference which exists between the two
processed branches of the radio link signal. When measuring the
delay difference between the two branches of an uplink radio
signal, a rake receiver (62) at the radio base station is employed.
On the other hand, when measuring the delay difference between the
two branches of a downlink radio signal, a rake receiver (262) at
test user equipment unit (30T) is employed.
Inventors: |
Sarresh; Lawrence (Kista,
SE), He; Ning (Sollentuna, SE), Ostman;
Thomas Leif (Spanga, SE) |
Assignee: |
Telefonaktiebolaget LM Ericsson
(publ) (Stockholm, SE)
|
Family
ID: |
21935597 |
Appl.
No.: |
10/045,024 |
Filed: |
January 15, 2002 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20030171139 A1 |
Sep 11, 2003 |
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Current U.S.
Class: |
455/562.1;
455/101; 455/226.1; 455/561 |
Current CPC
Class: |
H04B
7/0667 (20130101); H04B 7/0678 (20130101); H04B
7/084 (20130101); H04B 17/21 (20150115); H04B
7/0626 (20130101); H04B 17/10 (20150115); H04B
17/20 (20150115) |
Current International
Class: |
H04Q
7/20 (20060101) |
Field of
Search: |
;455/561,562.1,445,454,10,13.3,13.4,17,18,501,504,506,526,63.1,65,67.11,277.1,279.1,132,423,101
;370/203-213,320,334 ;375/147,148,260,267 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 938 204 |
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Aug 1999 |
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EP |
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1 069 713 |
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Jan 2001 |
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EP |
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95/15665 |
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Jun 1995 |
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WO |
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Other References
EP Search Report mailed Jul. 17, 2002. cited by other .
International Search Report mailed Apr. 1, 2003 in corresponding
PCT application No. PCT/SE03/00025. cited by other .
International Preliminary Examination Report mailed Feb. 11, 2004
in corresponding PCT Application No. PCT/SE03/00025. cited by
other.
|
Primary Examiner: Gelin; Jean
Attorney, Agent or Firm: Nixon & Vanderhye, P.C.
Claims
What is claimed is:
1. A method of operating a base station included in a radio access
network of a telecommunications system, the method comprising: (1)
obtaining, respectively from two diversity antennas for a
cell/carrier utilized in a sector served by the base station, two
branches of an uplink radio link signal, the radio link signal
being an unlink signal to the radio base station; (2) routing the
two branches of the radio link signal through two respective
branches of signal processing hardware subsequent to receipt of the
two branches of the unlink radio link signal from the respective
two diversity antennas; (3) using a rake receiver at the base
station for measuring a delay difference between the two branches
of the radio link signal; (4) using the delay difference to
determine a delay alignment adjustment value for compensating for
the delay difference between the two branches of the radio link
signal; performing steps (1) (3) with respect to radio link signals
involved in plural calls with plural user equipment units; after
step (3), determining an average of the plural delay difference
values with respect to the plural cells; and as step (4), using the
average delay difference to determine the delay adjustment
value.
2. The method of claim 1, further comprising: utilizing plural rake
receivers for measuring delay difference values between the two
branches of the radio link signals, at least one of the plural rake
receivers being utilized for plural cell/carriers; for each of the
plural rake receivers, storing, in a memory, the average of the
plural delay difference values measured for a specified
cell/carrier by the rake receivers; periodically accessing the
memory to obtain the average of the plural delay difference values
for each of the plural rake receivers for the specified
cell/carrier for calculating the delay alignment adjustment value
for the specified cell/carrier.
3. The method of claim 2, further comprising: for each of the
plural rake receivers, storing for each of the plural
cell/carriers, in a memory, an average of plural delay difference
values measured by the rake receivers; periodically accessing the
memory to obtain the average of the plural delay difference values
for each of the plural rake receivers on a per cell/carrier basis
for calculating the delay alignment adjustment value for each of
the plural cell/carriers.
4. The method of claim 1, further comprising applying the delay
alignment adjustment value to one of the two branches of signal
processing hardware to compensate for the delay difference.
5. The method of claim 4, further comprising applying the delay
alignment adjustment value to a delay alignment buffer included in
the one of the two branches of signal processing hardware to
compensate for the delay difference.
6. A method of operating a base station included in a radio access
network of a telecommunications system, the method comprising: (1)
obtaining, respectively from two diversity antennas for a
cell/carrier utilized in a sector served by the base station, two
branches of an uplink radio link signal; (2) routing the two
branches of the radio link signal through two respective branches
of signal processing hardware subsequent to receipt of the two
branches of the uplink radio link signal from the respective two
diversity antennas; (3) measuring a delay difference between the
two branches of the radio link signal; (A) performing steps (1) (3)
with respect to a radio link signal received from a test user
equipment unit which is situated essentially equidistantly between
the two diversity antennas, and thereby obtaining a hardware delay
value; (B) performing steps (1) (3) with respect to a radio link
signal received from a non-test user equipment unit which utilizes
the cell/carrier in the sector, and thereby obtaining a total delay
value; (C) using the total delay value and the hardware delay value
to determine an angle of arrival for the radio link signal received
from a non-test user equipment unit.
7. The method of claim 6, wherein step (C) further comprises: using
the total delay value and the hardware delay value to determine a
delay component attributable to the angle of arrival of the radio
link signal from the non-test user equipment unit; using the delay
component attributable to the angle of arrival of the radio link
signal from the non-test user equipment unit to determine an
arrival delay component the arrival delay component being
represented by a projection of a distance separating the two
diversity antennas on a direction of approach of the radio link
signal from the non-test user equipment unit; using the arrival
delay component to determine the angle of arrival.
8. The method of claim 6, further comprising: performing step (B)
and step (C) for plural non-test user equipment units which utilize
the cell/carrier in the sector; accumulating statistics pertaining
to the angle of arrival of radio link signals received by the
plural non-test user equipment units.
9. A base station included in a radio access network of a
telecommunications system and comprising: two diversity antennas
for a cell/carrier utilized in a sector served by the base station
from which are respectively obtained two branches of an uplink
radio link signal transmitted between the base station and a user
equipment unit; two branches of signal processing hardware at the
base station which respectively process the two branches of the
uplink radio link signal either before or after transmission
between the user equipment unit and the base station; and plural
rake receivers which, with respect to radio link signals involved
with plural calls with plural user equipment units, measure delay
difference values between the two branches of the plural radio link
signals, at least one of the plural rake receivers being utilized
for plural cell/carriers; a local memory for each of the plural
rake receivers in which is stored an average of plural delay
difference values measured for a specified cell/carrier by the rake
receivers; a processor which uses the delay difference to determine
a delay alignment adjustment value, and wherein the processor
periodically accesses the local memory to obtain the average of the
plural delay difference values for each of the plural rake
receivers for the specified cell/carrier for calculating the delay
alignment adjustment value for the specified cell/carrier.
10. The apparatus of claim 9, wherein each rake receiver is
situated on a board which has a board processor which computes the
average of plural delay difference values measured for the
specified cell/carrier; and wherein the processor which
periodically accesses the local memory is a main processor which is
distinct from the board processor.
11. The apparatus of claim 10, further comprising an array of rake
receivers each having a board processor which is periodically
accessed by the main processor.
12. The apparatus of claim 9, wherein the processor periodically
accesses the local memories for the plural rake receivers to obtain
the average of the plural delay difference values for each of the
plural rake receivers on a per cell/carrier basis for calculating
the delay alignment adjustment value for each of the plural
cell/carriers.
13. The apparatus of claim 12, wherein each rake receiver is
situated on a board which has a board processor which computes the
average of plural delay difference values measured for the
specified cell/carrier; and wherein the processor which
periodically accesses the local memory is a main processor which is
distinct from the board processor.
14. The apparatus of claim 9, wherein the delay alignment
adjustment value is applied to one of the two branches of signal
processing hardware.
15. The apparatus of claim 14, wherein the delay alignment
adjustment value is applied to a delay alignment buffer included in
the one of the two branches of signal processing hardware.
16. A radio access network of a telecommunications system
comprising: a base station having two diversity antennas for a
cell/carrier utilized in a sector served by the base station; a
test user equipment unit situated essentially equidistantly with
respect to the two diversity antennas, two branches of an uplink
radio link signal received from the test user equipment unit being
obtained respectively from the two diversity branches; the base
station further comprising: two branches of signal processing
hardware which respectively process the two branches of the radio
link signal; a rake receiver which measures a delay difference
between the two branches of the uplink radio link signal; a local
memory for the rake receiver in which is stored an average of
plural delay difference values measured for the cell/carrier by the
rake receiver; a processor which uses the delay difference to
determine a delay alignment adjustment value, and wherein the
processor periodically accesses the local memory to obtain the
average of the plural delay difference values for calculating the
delay alignment adjustment value for the cell/carrier.
17. The apparatus of claim 16, wherein the rake receiver is
situated on a board which has a board processor which computes the
average of plural delay difference values measured for the
cell/carrier; and wherein the processor which periodically accesses
the local memory is a main processor which is distinct from the
board processor.
18. The apparatus of claim 16, wherein the delay alignment
adjustment value is applied to one of the two branches of signal
processing hardware.
19. The apparatus of claim 18, wherein the delay alignment
adjustment value is applied to a delay alignment buffer included in
the one of the two branches of signal processing hardware.
20. A radio access network of a telecommunications system
comprising: a base station having two diversity antennas for a
cell/carrier utilized in a sector served by the base station; a
test user equipment unit situated essentially equidistantly with
respect to the two diversity antennas, two branches of a radio link
signal received from the test user equipment unit being obtained
respectively from the two diversity branches; the base station
further comprising: two branches of signal processing hardware
which respectively process the two branches of the radio link
signal; means for measuring a delay difference between the two
branches of the radio link signal; a non-test user equipment unit
which utilizes the cell/carrier in the sector, wherein the two
branches of signal processing hardware respectively process the two
branches of the radio link signal received from the non-test user
equipment unit; wherein the means for measuring measures a delay
difference between the two branches of the radio link signal for
the non-test user equipment unit to obtain a total delay value;
wherein the delay difference between the two branches of the radio
link signal measured for the test user equipment unit is used as a
hardware delay value; and further comprising an angle of arrival
determination unit which uses the total delay value and the
hardware delay value to determine an angle of arrival for the radio
link signal received from the non-test user equipment unit.
21. The apparatus of claim 20, wherein the angle of arrival
determination unit executes the steps of: (A) using the total delay
value and the hardware delay value to determine a delay component
attributable to the angle of arrival of the radio link signal from
the non-test user equipment unit; (B) using the delay component
attributable to the angle of arrival of the radio link signal from
the non-test user equipment unit to determine an arrival delay
component, the arrival delay component being represented by a
projection of a distance separating the two diversity antennas on a
direction of approach of the radio link signal from the non-test
user equipment unit; (C) using the arrival delay component to
determine the angle of arrival.
22. The apparatus of claim 21, wherein the angle of arrival
determination unit performs step (B) and step (C) for plural
non-test user equipment units which utilize the cell/carrier in the
sector; and accumulates statistics pertaining to the angle of
arrival of radio link signals received byte plural non-test user
equipment units.
23. A radio access network of a telecommunications system
comprising: a base station having two diversity antennas for a
cell/carrier utilized in a sector served by the base station; a
test user equipment unit situated essentially equidistantly with
respect to the two diversity antennas, two branches of a radio link
signal being transmitted between the test user equipment unit and
the two diversity antennas; the base station further comprising two
branches of signal processing hardware which respectively process
the two branches of the radio link signal; and wherein the test
user equipment unit measures a delay difference between the two
branches of the radio link signal and transmits a report of the
delay difference over an air interface to the base station.
24. The apparatus of claim 23, wherein the user equipment unit
comprises a rake receiver which measures the delay difference
between the two branches of the radio link signal.
25. The apparatus of claim 23, further comprising a processor at
the base station which uses the delay difference to determine a
delay alignment adjustment value.
26. The apparatus of claim 25, wherein the delay alignment
adjustment value is applied to one of the two branches of signal
processing hardware.
27. The apparatus of claim 26, wherein the delay alignment
adjustment value is applied to a delay alignment buffer included in
the one of the two branches of signal processing hardware.
28. The method of claim 23, further comprising using a rake
receiver at the user equipment unit for measuring the delay
difference between the two branches of the radio link signal.
29. The method of claim 23, further using the delay difference to
determine a delay alignment adjustment value.
30. The method of claim 29, further comprising applying the delay
alignment adjustment value to one of the two branches of signal
processing hardware.
31. The method of claim 30, further comprising applying the delay
alignment adjustment value to a delay alignment buffer included in
the one of the two branches of signal processing hardware.
32. A method of operating a telecommunications system, the method
comprising: routing two branches of a radio link signal through
corresponding two branches of signal processing hardware at a base
station and applying the two branches of the radio link signal
respectively to two diversity antennas at the base station;
transmitting the two branches of the radio link signal over an air
interface from the two diversity antennas to a test user equipment
unit, the test user equipment unit being situated essentially
equidistantly with respect to the two diversity antennas; at the
user equipment unit, measuring a delay difference between the two
branches of the radio link signal and transmitting a report of the
delay difference over an air interface to the base station.
Description
BACKGROUND
1. Field of the Invention
The present invention pertains to wireless telecommunications, and
particularly to diversity branch delay alignment in a sector of a
radio base station of a radio access network of a
telecommunications system.
2. Related Art and Other Considerations
In a typical cellular radio system, mobile user equipment units
(UEs) communicate via a radio access network (RAN) to one or more
core networks. The user equipment units (UEs) can be mobile
stations such as mobile telephones ("cellular" telephones) and
laptops with mobile termination, and thus can be, for example,
portable, pocket, hand-held, computer-included, or car-mounted
mobile devices which communicate voice and/or data with radio
access network.
The radio access network (RAN) covers a geographical area which is
divided into cell areas, with each cell area being served by a base
station. A cell is a geographical area where radio coverage is
provided by the radio base station equipment at a base station
site. Each cell is identified by a unique identity, which is
broadcast in the cell. The base stations communicate over the air
interface (e.g., radio frequencies) with the user equipment units
(UE) within range of the base stations. In the radio access
network, several base stations are typically connected (e.g., by
landlines or microwave) to a radio network controller (RNC). The
radio network controller, also sometimes termed a base station
controller (BSC), supervises and coordinates various activities of
the plural base stations connected thereto. The radio network
controllers are typically connected to one or more core
networks.
One example of a radio access network is the Universal Mobile
Telecommunications (UMTS) Terrestrial Radio Access Network (UTRAN).
The UMTS is a third generation system which in some respects builds
upon the radio access technology known as Global System for Mobile
communications (GSM) developed in Europe. UTRAN is essentially a
radio access network providing wideband code division multiple
access (WCDMA) to user equipment units (UEs). The Third Generation
Partnership Project (3GPP) has undertaken to evolve further the
UTRAN and GSM-based radio access network technologies.
As those skilled in the art appreciate, in W-CDMA technology a
common frequency baNd allows simultaneous communication between a
user equipment unit (UE) and plural base stations. Signals
occupying the common frequency band are discriminated at the
receiving station through spread spectrum CDMA waveform properties
based on the use of a high speed, pseudo-noise (PN) code. These
high speed PN codes are used to modulate signals transmitted from
the base stations and the user equipment units (UEs). Transmitter
stations using different PN codes (or a PN code offset in time)
produce signals that Can be separately demodulated at a receiving
station. The high speed PN modulation also allows the receiving
station to advantageously generate a received signal from a single
transmitting station by combining several distinct propagation
paths of the transmitted signal. In CDMA, therefore, a user
equipment unit (UE) need not switch frequency when handoff of a
connection is made from one cell to another. As a result, a
destination cell can support a connection to a user equipment unit
(UE) at the same time the origination cell continues to service the
connection. Since the user equipment unit (UE) is always
communicating through at least one cell during handover, there is
no disruption to the call. Hence, the term "soft handover." In
contrast to hard handover, soft handover is a "make-before-break"
switching operation.
The Universal Mobile Telecommunications (UMTS) Terrestrial Radio
Access Network (UTRAN) accommodates both circuit switched and
packet switched connections. In this regard, in UTRAN the circuit
switched connections involve a radio network controller (RNC)
communicating with a mobile switching center (MSC), which in turn
is connected to a connection-oriented, external core network, which
may be (for example) the Public Switched Telephone Network (PSTN)
and/or the Integrated Services Digital Network (ISDN). On the other
hand, in UTRAN the packet switched connections involve the radio
network controller communicating with a Serving GPRS Support Node
(SGSN) which in turn is connected through a backbone network and a
Gateway GPRS support node (GGSN) to packet-switched networks (e.g.,
the Internet, X.25 external networks). MSCs and GSNs are in contact
with a Home Location Register (HRL), which is a database of
subscriber information.
There are several interfaces of interest in the UTRAN. The
interface between the radio network controllers (RNCs) and the core
network(s) is termed the "Iu" interface. The interface between a
radio network controller (RNC) and its base stations (BSs) is
termed the "Iub" interface. The interface between the user
equipment unit (UE) and the base stations is known as the "air
interface" or the "radio interface" or "Uu interface". In some
instances, a connection involves both a Serving or Source RNC
(SRNC) and a target or drift RNC (DRNC), with the SRNC controlling
the connection but with one or more diversity legs of the
connection being handling by the DRNC. An Inter-RNC transport link
can be utilized for the transport of control and data signals
between Source RNC and a Drift or Target RNC, and can be either a
direct link or a logical link as described, for example, in
International Application Number PCT/US94/12419 (International
Publication Number WO 95/15665). An interface between radio network
controllers (e.g., between a Serving RNC [SRNC] and a Drift RNC
[DRNC]) is termed the "Iur" interface.
A base station is typically located near the center of its
associated cell. A base station can have plural sectors, with each
sector having one or more antenna. The antenna of each sector are
directed to cover a certain geographical portion of the cell. For
example, a cell may comprise three or six essentially Triangular
sectors, with the antenna of each sector positioned and directed to
cover the area of its triangular sector. The antenna of all sectors
are generally connected to hardware at a common base station
site.
Having more than one antenna per sector of a cell provides for
diversity branches of a link with a user equipment unit (UE) in
communication with the base station. Employment of diversity
antennas for a sector of a cell improves reception quality and (to
some extent) eliminates the effect of fading.
Using diversity antennas at a sector provides reception gain, as
more than one branch of the radio link with the user equipment unit
(UE) can be established. However, having two different branches
(with separate signal routes and hardware components with different
delay figures (mean value and variance)) results in delay
differences between the two branches and delay misalignment. Thus,
employment of diversity antennas also involves branch delay
differences. That is, the differing branches of the radio link may
have signals with corresponding differing arrival times and
differing signal processing delays, thereby making it difficult to
analyze collectively the signals of the respective branches to
obtain perhaps a more accurate resultant signal. These branch delay
differences are caused, at least in part, by an accumulation of
delay differences in different hardware components used to process
each branch. Each branch of the radio link is applied at the base
station to a series of hardware components for the branch. Although
the series of hardware components, and functions of the hardware
components, are essentially the same from one branch to another, as
a practical matter the individual hardware components do have
differing processing delay times.
Moreover, there are also delay difference components induced by
environmental conditions, equipment aging, and direction of arrival
of a signal. All these factors, individually or cumulatively, can
result in substantial delay differences between branches of a radio
link, which degrade or completely defeat any processing gain sought
by usage of diversity antennas.
In code division multiple access systems, a precise delay alignment
between the branches is necessary in order to obtain a reasonable
gain when using diversity antennas. Otherwise the gain from
diversity is negligible and not worth the complexity.
An attempt has previously been made to compensate for the delay
differences between branches of a radio link received by diversity
antennas at a sector of a base station. Typically the delay
differences are calculated based on certain hardware delay mean
values which are measured at the hardware factory and stored in a
memory (e.g., flash memory) on a board or the like which bears the
hardware. Also, delays occasioned by cabling (e.g., between
hardware components) is calculated according to cable type and
length. Using the stored delay differences for the hardware and the
cables, some type of compensation value is calculated and employed
to adjust the induced delay between the branches.
Unfortunately, the foregoing attempt to compensate for delay
differences entails substantial error. Factory measurement of
hardware delay may not be accurate, and in any event may differ
substantially from actual delay experienced due to non-factory
(e.g., installation at base station) environmental factors.
Moreover, temperature and equipment aging introduce relatively
serious errors in calculating a delay difference between two
branches. Further, any delay difference contribution owing to
differing direction of arrival of two branches is not taken into
account.
In order to make beneficial use of diversity antennas for a same
cell/carrier at a base station, the delay alignment precision
between the two diversity branches should be on the order of about
32.55 nanosecond. The better the alignment, the greater the
diversity gain. Yet the best precision that current techniques
(such as that aforedescribed) can muster is around 65
nanoseconds.
What is needed, therefore, and an object of the present invention,
is a technique for providing more accurate delay difference
precision between differing branches of a radio link for diversity
antennas of a sector of a cell.
BRIEF SUMMARY OF THE INVENTION
A base station included in a radio access network of a
telecommunications system has two diversity antennas for a sector
served by the base station which are respectively involved in
transmission of two branches of a radio link signal between the
base station and a user equipment unit. Two branches of signal
processing hardware respectively process the two branches of the
radio link signal to yield two respective processed branches of the
radio link signal. A rake receiver measures the delay difference
between the two processed branches of the radio link signal, and
uses the measured delay difference for various purposes.
For example, some embodiments of the invention use the delay
difference between the two branches as measured by the rake
receiver to compensate for a delay difference which exists between
the two processed branches of the radio link signal. When measuring
the delay difference between the two branches of an uplink radio
signal, a rake receiver at the radio base station is employed. On
the other hand, when measuring the delay difference between the two
branches of a downlink radio signal, a rake receiver at test user
equipment unit is employed.
In a first embodiment of the invention, a rake receiver measures
the delay difference between the two processed branches of the
uplink radio link signal. The delay difference is utilized (e.g.,
by a processor) to determine a delay alignment adjustment value.
The delay alignment adjustment value is applied to one of the two
branches of signal processing hardware, for example to a delay
alignment buffer included in one of the branches of signal
processing hardware which has the shortest delay prior to the
adjustment.
One example implementation of the first embodiment involves
measuring the delay difference between the two processed branches
of the radio link signals for plural calls (e.g., plural
connections), and preferably for plural user equipment units. In
this example implementation, plural rake receivers are utilized for
a sector. The plural rake receivers (which can be configured, e.g.,
as an array of rake receivers) are configured so that at least some
of the plural rake receivers can be utilized by plural sectors of
the radio base station. The rake receivers measure delay difference
values between the two processed branches of the radio link signal,
measuring the delay difference values for differing ones of the
plural sectors. A local memory provided for each of the plural rake
receivers stores an average of plural delay difference values
measured for a specified sector. A processor periodically accesses
the local memory to obtain the average of the plural delay
difference values for each of the plural rake receivers for the
specified sector, and uses the average delay difference value from
each rake receiver having a measurement for the specified sector to
calculate the delay alignment adjustment value for the specified
sector. In a variation of this implementation, the rake receiver is
situated on a receiver board which also bears a board processor
(which determines the average of the plural delay difference values
for the rake receivers on the receiver board) and the local memory.
The processor which periodically accesses the local memories is a
main processor of the radio base station which has access to each
of the receiver boards (which form a pool of receiver boards).
A second embodiment of the invention differs from the first
embodiment in that the two branches of the uplink radio link signal
are received by the two diversity antennas from a test user
equipment unit which is situated essentially equidistantly from the
two diversity antennas. The test user equipment unit is situated at
a close and substantially equal distance from the two diversity
antennas with a fairly good accuracy, i.e., a couple of
nanoseconds. As in the first embodiment, the rake receiver in the
receiver board measures the delay difference between the two
processed branches in each sector (e.g., for each antenna pair) for
the radio link which is established with the test user equipment
unit. The measurements performed by the rake receiver are performed
at a frequency defined by a service provider, and are stored in a
local memory. Thereafter, as in the first embodiment, the
measurements of the rake receiver are processed by a main
processor, which calculates the amount of adjustment needed between
the two branches. Again as in the first embodiment, the calculated
delay adjustment value is then sent to the delay alignment buffer
for the branch having the shortest delay prior to the
adjustment.
A third embodiment of the invention also uses the test user
equipment unit to determine diversity branch delay difference, and
for the further purpose of estimating an angle of arrival for the
signal received from other user equipment units. Having statistical
metrics on the angle of arrival distribution for user equipment
unit traffic generally can help a service provider optimize cell
planning and achieve more efficient utilization of the radio
frequency resources.
In essence, according to the third embodiment the delay skew
between two diversity branches of incoming signals from the user
equipment unit (UE) in the field are measured by rake receivers in
the receiver board, and compared with those transmitted by a test
user equipment unit (UE). As in the second embodiment, the test
user equipment unit (UE) is positioned essentially equidistantly
relative (preferably in front of) to the receive antennas, and the
delay difference measured by the rake receiver permits measurement
of a signal delay (delay.sub.HW) attributable to the hardware in
the respective hardware branches of the sector signal processing
section. The sector also receives radio link signals from non-test
(actual traffic) user equipment units, with the rake receiver also
measuring the delay difference for the diversity branches of the
processed radio link signal from the non-test user equipment units.
The measured delay difference for the diversity branches of the
processed radio link signal from the non-test user equipment units
is considered as a total delay (delay.sub.TOTAL). By subtracting
the hardware signal delay component (delay.sub.HW) discerned from
the test user equipment unit (UE) from the total delay
(delay.sub.TOTAL) discerned with respect to the non-test user
equipment units, a delay component attributable to the angle of
arrival (delay.sub.AOA) is determined. From the delay component
attributable to the angle of arrival (delay.sub.AOA), the angle of
arrival itself (AOA) is determined. The third embodiment allows the
service provider to obtain an estimate over the distribution angle
of arrival of the incoming signals to the radio base station's
receive antennas.
The fourth embodiment involves measuring downlink delay difference
a sector having plural diversity transmit antennas. Like the second
and third embodiments, the fourth embodiment utilizes a test user
equipment unit. In similar fashion to the sector receive signal
processing section, the sector transmit signal processing section
processes two branches of a downlink radio link signal to be
transmitted respectively by the two diversity antennas. Each branch
of hardware has a delay adjustment means (such as delay adjustment
buffer) and various signal processing hardware. In addition, the
sector transmit signal processing section includes a closed loop
downlink diversity branch delay alignment routine or unit which is
used to determine a delay alignment adjustment which can be sent to
the delay adjustment means for compensating any delay difference in
the transmit signal processing hardware of the two branches. Upon
starting, the closed loop downlink diversity branch delay alignment
routine sends a start signal to the test user equipment unit (UE).
Upon receiving the start signal from the closed loop downlink
diversity branch delay alignment routine, the rake receiver of the
test user equipment unit (UE) measures the delay difference on the
PDP pairs from two diversity branches on each branch of the
downlink radio signal in a specified measurement period. The test
user equipment unit (UE) sends a report of the delay difference
value to the closed loop downlink diversity branch delay alignment
routine, which in turn calculates a delay adjustment value for the
sector downlink signal processing section. The calculated delay
adjustment value is then applied to an appropriate one of the delay
adjustment means.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects, features, and advantages of the
invention will be apparent from the following more particular
description of preferred embodiments as illustrated in the
accompanying drawings in which reference characters refer to the
same parts throughout the various views. The drawings are not
necessarily to scale, emphasis instead being placed upon
illustrating the principles of the invention.
FIG. 1 is diagrammatic view of example mobile communications system
in which embodiments of the present invention may be advantageously
employed.
FIG. 2 is a diagrammatic view of a multi-sector base station site
having diversity antennas and a sector signal processing section
for each sector.
FIG. 3 is a schematic view of diversity antennas and a sector
signal processing section for an example sector.
FIG. 4 is a diagrammatic view of various functionalities included
in a receiver board.
FIG. 5 is a diagrammatic view showing an example implementation of
a base station site in which an array of receiver boards serves
plural sectors.
FIG. 6 is a schematic view of sector signal processing section for
an example sector for illustrating basic aspects of a first
embodiment of the invention.
FIG. 7A is a flowchart showing basic steps and events performed in
example implementations of an uplink analog delay alignment
procedure for a board processor and an uplink analog delay
alignment procedure for a rake receiver block.
FIG. 7B is a flowchart showing basic steps and events performed in
example implementations of an uplink analog delay alignment
procedure for a main processor of a base station site.
FIG. 8 is a diagrammatic view of an example format of a database
stored in a local memory of a receiver board.
FIG. 9 is a diagrammatic view of an example format of a database
stored in a main processor of a base station site.
FIG. 10 is a schematic view of sector signal processing section for
an example sector for illustrating basic aspects of a second
embodiment of the invention.
FIG. 11 is a diagrammatic view showing certain geometric
relationships and distances used to calculate an angle of arrival
for a sector having two diversity antennas.
FIG. 12 is a schematic view of sector signal processing section for
an example sector for illustrating basic aspects of a third
embodiment of the invention wherein angle of arrival is determined
for user equipment units in the field of the sector.
FIG. 13 is a flowchart showing certain basic steps and events
performed in the third embodiment.
FIG. 14 is a diagrammatic view of an example format of a database
maintained in conjunction with the third embodiment.
FIG. 15 is a schematic view of portions of a test user equipment
unit and a sector signal processing section for an example sector
for illustrating basic aspects of a forth embodiment of the
invention wherein a downlink diversity branch delay alignment
routine is performed.
FIG. 16 is a flowchart showing certain basic steps and events
performed in the fourth embodiment.
DETAILED DESCRIPTION OF THE DRAWINGS
In the following description, for purposes of explanation and not
limitation, specific details are set forth such as particular
architectures, interfaces, techniques, etc. in order to provide a
thorough understanding of the present invention. However, it will
be apparent to those skilled in the art that the present invention
may be practiced in other embodiments that depart from these
specific details. In other instances, detailed descriptions of
well-known devices, circuits, and methods are omitted so as not to
obscure the description of the present invention with unnecessary
detail. Moreover, individual function blocks are shown in some of
the figures. Those skilled in the art will appreciate that the
functions may be implemented using individual hardware circuits,
using software functioning in conjunction with a suitably
programmed digital microprocessor or general purpose computer,
using an application specific integrated circuit (ASIC), and/or
using one or more digital signal processors (DSPs).
FIG. 1 shows a non-limiting, example context of a universal mobile
telecommunications (UMTS) 10. A representative,
connection-oriented, external core network, shown as a cloud 12 may
be for example the Public Switched Telephone Network (PSTN) and/or
the Integrated Services Digital Network (ISDN). A representative,
connectionless external core network shown as a cloud 14, may be
for example the Internet. Both core networks are coupled to their
corresponding service nodes 16. The PSTN/ISDN connection-oriented
network 12 is connected to a connection-oriented service node shown
as a Mobile Switching Center (MSC) node 18 that provides
circuit-switched services. The Internet connectionless-oriented
network 14 is connected to a General Packet Radio Service (GPRS)
node 20 tailored to provide packet-switched type services which is
sometimes referred to as the serving GPRS service node (SGSN).
Each of the core network service nodes 18 and 20 connects to a UMTS
Terrestrial Radio Access Network (UTRAN) 24 over a radio access
network (RAN) interface referred to as the Iu interface. UTRAN 24
includes one or more radio network controllers (RNCs) 26. For sake
of simplicity, the UTRAN 24 of FIG. 1 is shown with only two RNC
nodes, particularly RNC 26.sub.1 and RNC 26.sub.2. Each RNC 26 is
connected to a plurality of base stations (BS) 28. For example, and
again for sake of simplicity, two base station nodes are shown
connected to each RNC 26. In this regard, RNC 26.sub.1 serves base
station 28.sub.1-1 and base station 28.sub.1-2, while RNC 26.sub.2
serves base station 28.sub.2-1 and base station 28.sub.2-2. It will
be appreciated that a different number of base stations can be
served by each RNC, and that RNCs need not serve the same number of
base stations. Moreover, FIG. 1 shows that an RNC can be connected
over an Iur interface to one or more other RNCs in the URAN 24.
Further, those skilled in the art will also appreciate that a base
station is sometimes also referred to in the art as a radio base
station, a node B, or B-node.
In the illustrated embodiments, for sake of simplicity each base
station 28 is shown as serving one cell. Each cell is represented
by a circle which surrounds the respective base station. It will be
appreciated by those skilled in the art, however, that a base
station may serve for communicating across the air interface for
more than one cell. For example, two cells may utilize resources
situated at the same base station site.
A user equipment unit (UE), such as user equipment unit (UE) 30
shown in FIG. 1, communicates with one or more cells or one or more
base stations (BS) 28 over a radio or air interface 32. Each of the
radio interface 32, the Iu interface, the Iub interface, and the
Iur interface are shown by dash-dotted lines in FIG. 1.
Preferably, but not necessarily, radio access is based upon
Wideband, Code Division Multiple Access (WCDMA) with individual
radio channels allocated using CDMA spreading codes. Of course,
other access methods may be employed. WCDMA provides wide bandwidth
for multimedia services and other high transmission rate demands as
well as robust features like diversity handoff and RAKE receivers
to ensure high quality.
In accordance with the present invention and as rudimentarily
illustrated in FIG. 2, a cell C served by a base station
(generically referenced as radio base station 28) included in the
radio access network 24 of telecommunications system 100 has one or
more sectors, with at least one of the sectors being served with
two (or more) diversity antennas. For sake of simplicity, FIG. 2
shows cell C as comprising six sectors, labeled as SECTOR 1 through
SECTOR 6. Cell C may have a greater or lesser number of sectors.
For each sector, the radio base station 28 includes a sector signal
processing section 40, which connects to the two diversity receive
antennas 44A and 44B for the sector. For example, SECTOR 1 has
sector signal processing section 40.sub.1 which is connected to
antennas 44A.sub.1 and 44B.sub.1.
It will be appreciated that FIG. 2 (and various other figures) is
not to scale, as the cell C and its comprising sectors is much
larger relative to the footprint of radio base station 28 than as
shown. Moreover, neither the number of sectors nor the
configuration (e.g., geographical extent or pattern) of the sectors
is a limiting aspect of the present invention. For example, the
sectors may be more geographically overlapping than as shown in
FIG. 2. Nor need the shape of cell C be circular (as shown only for
convenience and according to custom). The illustrative example of
FIG. 2 and other figures rather depicts fundamental principles of
the invention which are applicable broadly to various
configurations of radio base stations.
Each sector can have one or more radio frequency carriers. As used
herein, the notation "cell/carrier" denotes a particular
combination of cell and radio frequency carrier for that cell.
FIG. 3 shows in more detail a representative or example sector
signal processing section 40 of one example sector of radio base
station 28 (for which reason subscripts are not employed in FIG. 3)
which handles a cell/carrier of the sector. The sector signal
processing section 40 includes a sector signal processing front end
46, framed by a broken line in FIG. 3. The sector signal processing
front end 46 handles two branches of a radio link signal of the
cell/carrier, and accordingly has two branches of hardware. In
particular, sector signal processing front end 46 has a first
branch 47A of signal processing hardware ("Branch A") which handles
a first branch of the radio link signal which is obtained from
antenna 44A and a second branch 47B of signal processing hardware
("Branch B") which handles a second branch of the radio link signal
which is obtained from antenna 44B.
Each branch 47 of signal processing hardware includes a tower
mounted amplifier (TMA) 49 which is connected by a feeder 50 to its
respective antenna 44. The tower mounted amplifier (TMA) 49 is
connected to an input of an antenna interface unit (AI) 51, which
operates in conjunction with a multi-carrier power amplifier (MCPA)
52. An output of the antenna interface unit (AI) 51 is connected to
an input of a transceiver (TRX) 53, whose output is connected to an
input of a radio frequency interface board (RFIF) 54. An output of
the RFIF 54 is connected to a baseband interface board (BBIF) 56,
which in turn is connected by line 57 to a receiver board (RAX) 60.
A timing unit 58 is connected to the BBIF 56.
Each branch 47 of hardware included in sector signal processing
front end 46 has a delay adjustment means (such as delay adjustment
buffer 55) included in its transceiver (TRX) 53. For example,
branch 47A of sector signal processing front end 46 includes delay
adjustment buffer 55A situated in transceiver (TRX) 53A.
Embodiments of the invention utilize the delay adjustment means for
the purpose of compensating for a delay difference exists between
the two processed branches of the radio link signal.
The two branches 47A, 47B of signal processing hardware
respectively process the two branches of the radio link signal to
yield two respective processed branches of the radio link signal,
which are output from BBIF 56A and BBIF 56B as signals on lines 57A
and 57B, respectively.
Apart from sector signal processing front end 46, the sector signal
processing section 40 also includes the receiver board 60, also
know as a RAX board or RAX. As illustrated in FIG. 4, the receiver
board 60 includes one or more rake receivers 62 and (at least in
one implementation) a board processor 64. Up to as many as eight
rake fingers can be utilized per radio link.
Sector signal processing section 40 includes a main processor 70.
One function performed by main processor 70 which is germane to an
embodiment of the present invention is delay alignment, as depicted
by delay alignment function or unit 72. The main processor 70 and
the board processor 64 communicate with one another as depicted by
processor communication line 74.
As previously indicated, a sector can have one or more
cell/carriers. For purposes of facilitating understanding of the
present invention, it is sufficient to describe an example sector
having just one cell/carrier. For such simple case, the sector
signal processing structure of FIG. 3 can be taken as pertaining to
one cell/carrier. The person skilled in the art will understand
that signal processing structure such as that illustrated in FIG. 3
can be replicated for other cell/carriers for a sector having
plural cell/carriers. Alternatively, some of the components shown
in FIG. 3 can be utilized for plural cell/carriers.
The structure of each sector signal processing section 40 can
literally be as described above with respect to FIG. 2, e.g.,
comprising a dedicated sector signal processing front end 46, one
or more dedicated receiver boards 60, and a dedicated main
processor 70. In contrast, one implementation variation is to have
various non-front end elements of a sector signal processing
section 40 shared or pooled for access among several (perhaps even
all) cell/carriers of a radio base station, even for access for
cell/carriers of differing sectors of the radio base station. For
example, as one aspect of this example implementation, FIG. 5 shows
an example radio base station 28 having a pool or matrix of
receiver boards (RAXs) 80. As shown in FIG. 5, receiver board pool
80 comprises receiver boards 60.sub.a through 60.sub.k. At least
some, and perhaps all, of the receiver boards 60 in receiver board
pool 80 are available to serve, at differing times, differing
cell/carriers of radio base station 28, including cell/carriers of
differing sectors of the radio base station. For example, receiver
board 60.sub.a may at one moment in time be allocated to serve a
cell/carrier of SECTOR 1, and subsequently allocated to serve a
cell/carrier of SECTOR 4. Therefore, there is not necessarily any
direct permanent correspondence between any receiver board 60 and
any sector or cell/carrier.
As another and separable aspect of this example implementation of
FIG. 5, the example radio base station 28 has a main processor 70
which serves plural sectors (e.g., preferably all sectors), and
thus plural cell/carriers. The main processor 70 of FIG. 5 includes
a delay alignment function or unit 72 which accordingly serves the
plural cell/carriers of the plural sectors. In the FIG. 5
implementation, the processor communication line 74 comprises a bus
or the like which connects main processor 70 with the board
processors 64 provided on the respective receiver boards 60 in
receiver board pool 80.
In the FIG. 5 implementation, receiver board pool 80 and
(optionally) main processor 70 are shown as serving plural
cell/carriers, and preferably cell/carriers of all sectors of cell
C. To this end, FIG. 5 shows that each sector retains its own
dedicated sector signal processing front end 46, with the lines 57
emanating therefrom connecting to receiver board pool 80. Although
in the illustrated example embodiment all receiver boards 60 are
connected to handle all cell/carriers, main processor 70 instructs
each receiver board 60 individually as to which cell/carrier the
receiver board is to listen and utilize. It will be appreciated
that, in other embodiments, there could be other ways of applying a
cell/carrier to a particular receiver board 60, e.g., a selective
routing of cell/carrier to a particular receiver board 60.
In essence, in the FIG. 5 implementation, the sector signal
processing front ends 46 are dedicated for each sector, while the
remainder of the sector signal processing section 40 for each
sector is shared or pooled (using, e.g., one or both of receiver
board pool 80 and main processor 70). As indicated above, the
receiver board 60 can be dedicated to a sector signal processing
section 40 in the manner suggested (but not required) by FIG. 3, or
situated in receiver board pool 80 as shown in the implementation
of FIG. 5.
FIG. 6 shows basic aspects of a first example embodiment. In the
first embodiment, for a specified cell/carrier a rake receiver 62
allocated to the cell/carrier measures the delay difference between
the two processed branches of the radio link signal, e.g., between
the signals on lines 57A, 57B. Such measurement of delay difference
is depicted as event 6-1 in FIG. 6. The delay difference is
utilized (e.g., by a processor) to determine a delay alignment
adjustment value. In the embodiment of FIG. 6, event 6-2 shows the
measured delay difference (or a value derived therefrom, such as an
average or weighted average delay difference) being transmitted to
main processor 70. Event 6-3 shows main processor 70, and
particularly delay alignment unit 72, using the delay difference to
calculate a delay alignment adjustment. As event 6-4, the delay
alignment adjustment value is applied to one of the two branches of
signal processing hardware, for example to one of the delay
alignment buffers 55A, 55B included in one of the branches 47A, 47B
of signal processing hardware. In the particular situation shown in
FIG. 6, the delay alignment adjustment value happens to be applied
to branch 47B since it is the branch which (prior to the adjustment
application) had the shortest delay, and particularly to delay
adjustment buffer 55B.
How the delay adjustment value transmitted, e.g., as event 6-4,
affects a delay alignment buffer 55 depends on particular
configuration and implementation of the buffer. For example, delay
alignment buffer 55 can be a variable delay buffer which receives a
control signal, the content or value of the control signal
controlling the duration of the delay caused by the buffer. As an
example, if the control signal is utilized to write a value of
"100" to the variable delay buffer 55, the buffer 55 will generate
100 units of delay. Each unit is Tchip/16, which is almost 16.25
nanoseconds. The delay is generated by propagating the signal
through the cells of the buffer, with each propagation step being
one unit.
One example mode of the first embodiment, e.g., the general
embodiment of FIG. 6, can be carried out in the context of the
radio base station implementation of FIG. 5. In this mode, plural
rake receivers 62 (which can, for example, comprise the receiver
board pool 80 with each receiver board 60 having a rake receiver
62) are configured so that at least some of the plural rake
receivers can be utilized by plural cell/carriers of the radio base
station. As in the case of FIG. 6, for a cell/carrier to which it
is allocated (e.g., temporarily allocated), at specified intervals
a given rake receiver measures the delay difference value between
the two processed branches of the radio link signal for the
allocated cell/carrier. In this example mode, for one or more
cell/carriers the delay difference is measured with respect to the
branches of radio link signals for plural calls (e.g., plural
connections), preferably involving plural user equipment units.
A processor associated with the given rake receiver (such as board
processor 64) computes an average of plural delay difference values
measured for a specified cell/carrier. A local memory provided for
each of the plural rake receivers 62, e.g., board processor 64 or a
memory controlled by board processor 64, stores the calculated
average of plural delay difference values measured for the
allocated cell/carrier. Then, corresponding to event 6-2 in FIG. 6,
a processor (such as main processor 70) periodically accesses the
local memory to obtain the average of the plural delay difference
values for each of the plural rake receivers for the specified
cell/carrier. Further, corresponding to event 6-3, the processor
(e.g., delay alignment unit 72) uses the average delay difference
value from each rake receiver having a measurement for a specified
cell/carrier to calculate the delay alignment adjustment value for
the specified cell/carrier. The delay alignment adjustment value is
then communicated to the appropriate hardware in the manner
generally described as event 6-4 in FIG. 6.
To implement the example mode summarized above, certain basic
actions or steps must be performed by each of rake receiver 62,
board processor 64, and main processor 70. Pertinent ones of such
basic actions or steps are illustrated in example form for board
processor 64 and rake receiver 62 in FIG. 7A, and for main
processor 70 in FIG. 7B. As used herein, "rake receiver 62"
includes an uplink base band processing (UBP) rake receiver block.
The UBP rake receiver block, herein generally referred to as rake
receiver 62, is a set of rake fingers which are assigned by a
demodulator to different phase shifts in time (delays) or power
delay profiles ("PDPs"). Each PDP represents the delay/phase shift
in time for each rake finger. There is one PDP for each branch and
each connection/link at a given time.
In showing general steps pertinent to the present invention for the
uplink analog delay alignment procedure performed by board
processor 64, FIG. 7A shows board processor 64 receiving as action
7A-1 a request to start measurements and certain related parameters
which are necessary for performing the measurements. Included among
the received parameters are the Nr_Of_Samples Per_Call_Threshold
parameter and the Nr_Of_Samples_Per_Call_Ceiling parameter. The
parameter Nr_Of_Samples_Per_Call_Threshold defines the minimum
Nr_Of_Samples of measurement that a call needs in order to quality
the call to qualify for being reported from the rake receiver block
to the board processor 64 (otherwise the measurement is discarded).
The parameter Nr_Of_Samples_Per_Call_Ceiling defines the maximum
Nr_Of_Samples of measurement before the call will get reported from
the rake receiver block to the board processor 64. As explained
subsequently, a report for a call with a larger number of samples
than Nr_Of_Samples_Per_Call_Ceiling is broken or segmented into
plural reports, each having a number of samples no more than
Nr_Of_Samples_Per_Call_Ceiling.
As action 7A-2, the board processor 64 commissions the rake
receiver block to make measurements on the power delay profiles
(PDPs) obtained for the two branches of a radio link. After so
commissioning the rake receiver block, in its uplink analog delay
alignment procedure the board processor 64 waits until receipt of a
report from the rake receiver block, such receipt being shown as
action 7A-3.
Before describing how the uplink analog delay alignment procedure
as performed by board processor 64 uses the report obtained from
the rake receiver block, the uplink analog delay alignment
procedure as performed by the rake receiver block is next described
with reference to FIG. 7A. Although not shown in FIG. 7A, various
parameters are initialized upon the commissioning of execution of
the uplink analog delay alignment procedure by the block, such as
the parameter Nr_Of_Samples, for example. Moreover, it will be
understood that, in conjunction with the commissioning of action
7A-2, various parameters were passed to the rake receiver block.
Among these passed parameters are the radio link ID and
cell/carrier ID which respectively specify the radio link (e.g.,
connection) and cell/carrier (e.g., antenna pair) involved in the
commissioned measurements.
As action 7A-4, the rake receiver block takes a sample of the
delay/phase shift (e.g., PDP) for each branch of the connection
(e.g., for each branch of the radio link signal). After taking the
sample of action 7A-3, the counter Nr_Of_Samples is incremented at
action 7A-5. The delay measurement sample taken at action 7A-4 is
added to a running total of delay for the call and cell/carrier,
and using such cumulative total and the Nr_Of_Samples parameter, at
action 7A-6 an average delay sample value is computed by the rake
receiver block.
A determination is then made at action 7A-7 whether a release of
the currently sampled radio link (e.g., connection) has occurred.
If a release of the radio link has not occurred, at an appropriate
interval the uplink analog delay alignment procedure performed by
the block returns to action 7A-4 for taking another sample. If a
release of the radio link has occurred, post-release processing is
performed beginning with action 7A-8.
At action 7A-8 the uplink analog delay alignment procedure executed
by the rake receiver block determines whether the Nr_Of_Samples is
less than the Nr_Of_Samples_Per_Call_Threshold. If the
determination at action 7A-8 is negative, as action 7A-9 the
measurements for the call are discarded. If the determination at
action 7A-8 is positive, the uplink analog delay alignment
procedure performed by the rake receiver block determines whether
the results for the call can be reported in a single report, or
whether the Nr_Of_Samples for the call is so great as to require
that the call be considered as plural calls, for which a separate
report will be generated for each of the so-considered plural
calls.
As action 7A-10, the rake receiver block ascertains whether the
Nr_Of_Samples exceeds the Nr_Of_Samples Per Call_Ceiling parameter.
If the determination at action 7A-10 is negative, then (as
reflected by action 7A-11) the call will be treated as a single
call (e.g, the Nr_Of_Calls parameter is set equal to one). On the
other hand, if the determination at action 7A-10 is positive, for
reporting purposes at action 7A-12 the call will be segmented into
plural calls (e.g., effectively treated as plural connections). The
action 7A-12 shows that a parameter Nr_Of_Calls is calculated. The
Nr_Of_Calls parameter is the total number of calls on which a delay
difference in each sector and receiver board 60 has been measured.
After the determination of action 7A-12, as shown by action 7A-13 a
report regarding the uplink analog delay alignment procedure for
the rake receiver block is prepared and transmitted to main
processor 70. The report of action 7A-13 includes, e.g., the
Nr_Of_Samples, the average delay sample value, and Nr_Of_Calls.
As an example of execution of action 7A-12, consider a call which
has a number of samples (Nr_Of_Samples) which is more than the
Nr_Of_Samples_Per_Call_Ceiling parameter, for example, a number of
samples which is 1.7 times the Nr_Of_Samples_Per_Call_Ceiling
parameter. In accordance with the logic of the uplink analog delay
alignment procedure for the rake receiver block as above described,
the call will be regarded (e.g., at action 7A-12) as two calls: a
first call having a number of samples equal to the
Nr_Of_Samples_Per_Call_Ceiling parameter, and a second call having
a number of samples equal to 0.7 times the
Nr_Of_Samples_Per_Call_Ceiling parameter.
After receiving at action 7A-3 the report from the rake receiver
block, as action 7A-14 the uplink analog delay alignment procedure
performed by board processor 64 uses the report to calculate a
running weighted average of delay values. The calculation of action
7A-14 is based on a previous running weighted average of delay
values, plus the average delay sample value, the Nr_Of_Samples
weight, and the Nr_Of_Calls parameter included in the report of
action 7A-13. The values are only calculated per calculation
instance based on the reports from all RAX boards at that specific
time.
As action 7A-15, the uplink analog delay alignment procedure
performed by board processor 64 updates its cumulative count of the
Nr_Of_Calls. Then, as action 7A-16, the board processor 64 updates
a database or matrix which it maintains.
An example format for the database or matrix maintained by board
processor 64 is illustrated in FIG. 8. For each cell/carrier, the
database includes the following pertinent fields: an average delay
value; Nr_Of_Samples, and Nr_Of_Calls. The example database of FIG.
8 shows storage of information for j number of cell/carriers
handled by the corresponding receiver board (RAX) 60.
FIG. 7B shows general steps and actions performed by the uplink
analog delay alignment procedure executed by main processor 70, and
particularly by delay alignment unit 72. The action 7B-1 of FIG. 7B
depicts the start of the uplink analog delay alignment procedure
executed by (or primarily by) delay alignment unit 72. Upon
starting, the uplink analog delay alignment procedure reads the
delay data matrix maintained by each receiver board 60 (more
particularly, maintained by each board processor 64). An example of
such delay data matrix has been previously described with reference
to FIG. 8, for example. For each cell/carrier and each RAX (e.g.,
receiver board 60), at action 7B-2 the delay alignment unit 72
obtains the average delay value; the Nr_Of_Samples, and the
Nr_Of_Calls. Upon receiving such data from all receiver boards 60
included in the receiver board pool 80, as action 7B-3 the delay
alignment unit 72 constructs or forms its own delay data matrix. An
example format for such delay data matrix formed by delay alignment
unit 72 is illustrated in FIG. 9.
The matrix of FIG. 9 is a three dimensional matrix. In the matrix
of FIG. 9, a first dimension shown as the vertical dimension is
associated with cell/carriers. For example, the first horizontal
row at the top of the matrix is associated with a first
cell/carrier, the second horizontal row therebeneath is associated
with a second cell/carrier, and so on. The database of FIG. 9 shows
storage of information for x number of cell/carriers. A second
dimension shown as the horizontal dimension in FIG. 9 is associated
with RAXes (e.g., receiver boards 60). For example, a first slice
along the depth of the matrix contains data collected from a first
receiver board 60.sub.a, a second slice (to the right of the first
slice moving to the right in FIG. 9) contains data collected from a
second receiver board 60.sub.b, and so forth. Each slice
essentially resembles the matrix of FIG. 8 as maintained by the
respective receiver board 60. The data of the matrix resides in the
depth dimension of the matrix. The data items include those of the
matrix of FIG. 8, e.g., the average delay value, the Nr_Of_Samples,
and the Nr_Of_Calls.
Many of the remaining actions of the uplink analog delay alignment
procedure as described in FIG. 7B are performed based on the data
stored in the matrix maintained by delay alignment unit 72 (an
example of which appears in FIG. 9). As described hereinbelow, the
data is accessed in terms of cell/carriers and RAX boards (e.g.,
receiver boards 60).
As action 7B-4, the uplink analog delay alignment procedure
determines the frequency of measurements to be made (and thus the
frequency with which alignment values are to be applied to the
sector signal processing section 40). Such frequency is determined
by consulting a parameter BRANCH_DIFF_Timer. The BRANCH_DIFF_Timer
is set or otherwise input by a service provider and defines the
frequency with which the measurements are read by delay alignment
unit 72 from the receiver board 60. As part of action 7B-4, the
delay alignment unit 72 initializes its internal timer
T.sub.Branch.sub.--.sub.diff.sub.--.sub.Timer to the value of
BRANCH_DIFF_Timer.
The actions 7B-6 to and including action 7B-15 form a loop, with
certain actions of the loop, as appropriate, being performed for
each cell/carrier of the radio base station. In other words, each
execution of the loop of actions 7B-6 to and including action 7B-15
is associated with a particular cell/carrier of the radio base
station. The loop begins with action 7B-6, and is followed by
certain initialization steps performed as action 7B-7. Among the
initialization steps performed as action 7B-7 are those of
initializing the parameters Total_Delay and Total_Nr_Of_Samples at
zero. The Nr_Of_Samples is the total number of measured delay
difference samples for each sector and RAX. The Total_Delay is the
sum of all delay differences for one cell/carrier during one report
period.
After the initialization of action 7B-7, the uplink analog delay
alignment procedure performed by delay alignment unit 72 executes a
nested loop comprising action 7B-8 through and including action
7B-12. Each execution of the loop comprising action 7B-8 through
and including action 7B-12 pertains to a particular one of the
receiver boards (RAXs) 60. Being nested in the cell/carrier loop
(extending from action 7B-6 to action 7B-15), the steps of the
nested loop are thus performed relative both to cell/carrier and
RAX.
As action 7B-9, a determination is made whether the Nr_Of_Samples
exceeds the Nr_Of_Samples_Threshold. The Nr_Of_Samples_Threshold is
a parameter which defines the minimum number of samples (e.g., the
minimum value for Nr_Of_Samples) required from each cell/carrier in
each RAX board in order for the measurement from that certain
cell/carrier and that RAX to be included in the measurement
reports. If the determination at action 7B-9 is positive, action
7B-10 and action 7B-11 are performed before reaching action 7B-12.
At action 7B-10, the value for Total_Delay is updated, while at
action 7B-12 the value of the parameter Nr_Of_Samples is updated.
The nested loop comprising action 7B-8 through and including action
7B-12 is performed for each RAX board (e.g., for each receiver
board 60 in receiver board pool 80, or at least for those
appropriate). At action 7B-12 the uplink analog delay alignment
procedure checks whether all such RAX boards have been taken into
consideration, and (if not) repeats the nested loop for the next
RAX board by returning to action 7B-8. When all RAX boards have
been processed for a sector, processing continues with action
7B-13.
The following logic exemplifies the calculations performed by
action 7B-10 and action 7B-11:
For RAX_Nr=1 to Max_RAX_Nr If
(A[cell/carrier_ID,RAX_Nr].Nr-Of-Samples>Nr_Of_Samples_Threshold
and
A[cell/carrier_ID,RAX_Nr].Nr_Of_Calls>Nr_Of_Calls_Threshold),
then
Total_Delay=Total_Delay+A[cell/carrier_ID,RAX_Nr].Delay*A[cell/carrier_ID-
,RAX_Nr].Nr_Of_Samples
Total_Nr_Of_Samples=Total_Nr_Of_Samples+A[cell/carrier,RAX_Nr].Nr_Of_Samp-
les Endif
In the foregoing, parameters not yet described have the following
meanings: RAX_Nr identifies a particular RAX board (e.g., receiver
board 60). MAX_RAX_Nr defines the number of RAX boards for which
the nested loop is appropriate (e.g., likely k number of RAX
boards, such being the number in the receiver board pool 80).
Nr_Of_Calls_Threshold is a threshold which defines the minimum
number of calls (Nr_Of_Calls) required for each report from each
cell/carrier in each RAX board in order for the measurement from
that certain cell/carrier within that certain RAX to be included in
the measurement reports.
The action 7B-13, performed after the nested loop has been
performed for all RAX boards (e.g., receiver boards 60), involves
loading the total delay accumulated for a cell/carrier (with data
from all RAX boards now having been taken into consideration) into
an array Total_Delay(cell/carrier). Similarly, as action 7B-14, the
Nr_Of_Samples accumulated for the cell/carrier is stored in an
array Nr_Of_Samples(cell/carrier).
The action 7B-15 involves the delay alignment unit 72 checking
whether the loop comprising action 7B-6 to and including action
7B-15 has been performed for all cell/carriers. If other
cell/carriers remain for processing, another execution of the loop
is performed (e.g., processing returns to action 7B-6). When all
cell/carriers have been processed, execution resumes at action
7B-16.
The action 7B-16 actually beings another cell/carrier-based loop.
Such second cell/carrier-based loop commences with action 7B-16 and
continues through and including action 7B-21. After the loop is
begun (action 7B-16), at action 7B-17 the delay alignment unit 72
calculates, for a cell/carrier which is a subject of the particular
iteration of the loop, a delay difference between the two branches.
In other words, for action 7B-17 the delay alignment unit 72
performs a calculation such as the following:
T.sub.Branch.sub.--.sub.diff(cell/carrier)=Total_Delay(cell/carrier)/Tota-
l_Nr_Of_Samples(cell/carrier)
After calculating the delay difference between branches for a
cell/carrier, as action 7B-18 a check is made whether the delay
difference between branches for a sector (e.g.,
T.sub.Branch.sub.--.sub.diff(cell/carrier)) exceeds a threshold
(T.sub.Branch.sub.--.sub.diff.sub.--.sub.Threshold). The parameter.
T.sub.Branch.sub.--.sub.diff.sub.--.sub.Threshold is the smallest
delay difference required for attempting to update the delay
adjustment value in the delay adjustment buffer 55. If the
determination at action 7B-18 is positive, e.g., if the threshold
(T.sub.Branch.sub.--.sub.diff.sub.--.sub.Threshold) is exceeded,
action 7B-19 and action 7B-20 are performed prior to performing
action 7B-21. Otherwise, if the determination at action 7B-18 is
negative, e.g., if the threshold
(T.sub.Branch.sub.--.sub.diff.sub.--.sub.Threshold) is not
exceeded, action 7B-21 is immediately performed.
At action 7B-19 the delay adjustment value for the cell/carrier can
be updated using a generalized calculation such as the following:
T.sub.TRX.sub.--.sub.RF.sub.--.sub.UL[cell/carrier+0]=T.sub.TRX.sub.--.su-
b.RF.sub.--.sub.UL[cell/carrier+0]+T.sub.Branch.sub.--.sub.diff[cell/carri-
er+0]
A more accurate procedure for updating the delay adjustment value
is reflected by the steps shown in Table 1.
At action 7B-20, the delay adjustment value, e.g.,
T.sub.TRX.sub.--.sub.RF.sub.--.sub.UL[Sector+0], is sent to the
hardware. Reference is again made to event 6-4 in the example of
FIG. 6, wherein the delay adjustment value is applied to one of the
delay adjustment buffers 55 in the sector signal processing section
40, e.g., the buffer 55 which, prior to the adjustment, had the
shortest delay value.
The action 7B-21 involves a check whether the loop comprising
action 7B-16 through and including action 7B-21 has been performed
for all cell/carriers. If not, execution returns to action 7B-16
for the next cell/carrier to be processed. Otherwise, when all
cell/carriers have been processed, execution proceeds to action
7B-22.
At action 7B-22 the timer (T.sub.Branch.sub.--.sub.diff-Timer) is
consulted. This timer was initialized at action 7B-4, and indicates
the frequency with which, e.g., adjustments are to be performed. If
the timer has not yet timed out, the uplink analog delay alignment
procedure waits as indicated at action 7B-23 until timeout. When
the timer (T.sub.Branch.sub.--.sub.diff-Timer) has timed out, the
uplink analog delay alignment procedure is again executed by delay
alignment unit 72. Such repeated execution is depicted in FIG. 7B
by a return to action 7B-1.
The delay adjustment means included in the sector signal processing
front end 46 has been described in the aforementioned embodiments
as taking an example form of a delay adjustment buffer. Other
suitable implementations are also encompassed.
FIG. 3 shows certain examples of components included in a
particular implementation of the signal processing hardware of a
sector signal processing front end. The present invention is not
limited by the exact identity, nature, or arrangement of components
included in the signal processing hardware of a sector signal
processing front end 46.
The first embodiment of the invention thus achieves a better
precision in delay alignment. As noted above, the rake receiver in
the RAX board 60 is employed to measure the delay difference
between the two branches for each cell/carrier (e.g., the antenna
pair) for each radio link. The invention provides enhanced
accuracy, e.g., within a couple of nanoseconds. The measurements
are executed frequently and could be executed essentially
constantly. The timing of the measurements is configurable and can
be configured, e.g., such that it would only to measure essentially
constantly. The measurements are stored in a matrix by the receiver
board 60 in the manner shown in FIG. 9. Thereafter, these
board-based measurements are processed by main processor 70, and
more particularly by delay alignment unit 72, to obtain the delay
adjustment values for each cell/carrier. The calculated delay
adjustment values are sent to the delay adjustment buffer 55 for
the appropriate branch. Accordingly, the residual delay difference
after the alignment is equal to the following expression:
Measurement accuracy+Adjustment step size+angle of arrival
variance.
Whereas at least one example of the first embodiment envisions
measuring the delay difference with respect to branches of radio
link signals for plural calls (e.g., plural connections),
preferably involving plural user equipment units, a second
invention measures the delay difference with respect to two
branches of a radio link signal emanating from a test user
equipment unit. The test user equipment unit is situated at a close
and substantially equal distance from the two diversity antennas
with a fairly good accuracy, i.e., a couple of nanoseconds. In
other words, the test user equipment unit is situated essentially
equidistantly from the two diversity antennas.
FIG. 10 shows basic aspects of the second embodiment of the
invention, including the test user equipment unit 30T which is
situated essentially equidistantly between the two diversity
antennas 44A and 44B of a sector. For the specified cell/carrier
involved in the test or calibration, the rake receiver 62 allocated
to the cell/carrier measures the delay difference between the two
processed branches of the radio link signal emanating from the test
user equipment unit 30T, e.g., measures the delay difference
between the signals on lines 57A, 57B. The remaining operations of
the second embodiment are essentially similar to those of the first
embodiment (FIG. 6), it being understood that a substantial
difference is that the second embodiment makes the delay difference
measurements only with respect to the test user equipment unit 30T
(rather than with respect to plural user equipment units, as
occurred in at least one mode of the first embodiment). Such
measurement of delay difference for the second embodiment is
depicted as event 10-1 in FIG. 10. The delay difference is utilized
(e.g., by a processor) to determine a delay alignment adjustment
value. Event 10-2 shows the measured delay difference (or a value
derived therefrom, such as an average or weighted average delay
difference) being transmitted to main processor 70. Event 10-3
shows main processor 70, and particularly delay alignment unit 72,
using the delay difference to calculate a delay alignment
adjustment. As event 10-4, the delay alignment adjustment value is
applied to the appropriate one of the two branches of signal
processing hardware, for example to delay alignment buffers 55B
included in branch 47B of the signal processing hardware.
A third embodiment of the invention also uses the test user
equipment unit 30T to determine diversity branch delay difference,
and for the further purpose of estimating an angle of arrival for
the signal received from other user equipment units. Having
statistical metrics on the angle of arrival distribution for user
equipment unit traffic generally can help a service provider
optimize cell planning and achieve more efficient utilization of
the radio frequency resources. Traditionally there has been no
precise measurement on the distribution of the angle of arrival at
the base station, and consequentially cell planning is based on a
rough estimate made prior to putting up the radio base station and
using inaccurate empirical criteria.
The third embodiment allows the service provider to obtain an
estimate over the distribution angle of arrival of the incoming
signals to the radio base station's receive antennas. In essence,
according to the third embodiment the delay skew between two
diversity branches of incoming signals from the user equipment unit
(UE) in the field are measured by rake receivers in the receiver
board 60, and compared with those transmitted by a test user
equipment unit (UE). As in the second embodiment, the test user
equipment unit (UE) is positioned essentially equidistantly
relative (preferably in front of) to the receive antennas, and the
delay difference measured by the rake receiver permits measurement
of a signal delay (delay.sub.HW) attributable to the hardware in
the respective hardware branches of the sector signal processing
section 40. The sector also receives radio link signals from
non-test (actual traffic) user equipment units, with the rake
receiver also measuring the delay difference for the diversity
branches of the processed radio link signal from the non-test user
equipment units. The measured delay difference for the diversity
branches of the processed radio link signal from the non-test user
equipment units is considered as a total delay (delay.sub.TOTAL).
By subtracting the hardware signal delay component (delay.sub.HW)
discerned from the test user equipment unit (UE) from the total
delay (delay.sub.TOTAL) discerned with respect to the non-test user
equipment units, a delay component attributable to the angle of
arrival (delay.sub.AOA) is determined. From the delay component
attributable to the angle of arrival (delay.sub.AOA), the angle of
arrival itself (AOA) is determined.
FIG. 12 and the flowchart of FIG. 13 show certain basic aspects of
the third embodiment of the invention. In one implementation of the
invention, the actions reflected by FIG. 13 are implemented by the
receiver board 60, with certain measurements hereinafter described
performed by the rake receiver 62 and calculations performed by an
angle of approach determination unit 64-12. In one alternative
implementation of the invention, the angle of approach
determination unit 64-12 can take the form of board processor 64,
previously described.
Like in the second embodiment, in the third embodiment the test
user equipment unit 30T is situated essentially equidistantly
between the two diversity antennas 44A and 44B of a sector. But
unlike the second embodiment, the third embodiment involves other
user equipment units (UE) as well, particularly illustrated as
non-test user equipment units 30-1 and 30-2 which are present in
the same sector and which use the same cell/carrier as the test
user equipment unit 30T. For sake of simplicity, only two non-test
user equipment units (UE) 30 are shown in FIG. 12, it being
understood that another number (e.g., likely a greater number) of
user equipment units (UE) are served by the sector of interest at
any given time.
As in the second embodiment, in the third embodiment the rake
receiver 62 allocated to the cell/carrier utilized by the test user
equipment unit (UE) 30T measures the delay difference between the
two processed branches of the radio link signal emanating from the
test user equipment unit 30T. Such measurement of delay difference
with respect to the test user equipment unit (UE) 30T for the third
embodiment is depicted as event 13-1 in FIG. 12 and FIG. 13.
The third embodiment also involves measurement of the delay
difference between the two processed branches of the radio link
signals emanating from the non-test user equipment units (e.g., UE
30-1 and UE 30-2). The processing of the non-test user equipment
units (UE) is depicted in the flowchart of FIG. 13 by a loop which
commences with action 13-2 through and including action 13-9.
The action 13-2 reflects handing of the first non-test user
equipment unit (UE) (or, for subsequent executions of the non-test
loop, a next non-test user equipment unit (UE) to be processed). As
action 13-3, the rake receiver 62 measures the delay difference
between the two processed branches of the non-test user equipment
unit (UE) (e.g., one of UE 30-1 and 30-2 in FIG. 12) to obtain a
total delay (delay.sub.TOTAL) for that particular non-test user
equipment unit (UE). The measurement of action 13-3 is performed in
virtually the same manner as that of action 13-1, it being
understood however that the measurement of action 13-1 was for the
test user equipment unit (UE) 30T, while the measurement of action
13-3 is for the non-test user equipment unit (UE).
Various other actions included in the non-test UE loop of FIG. 13
are understood with reference to the geometric depiction of FIG.
11. If the elevation angle is neglected, the azimuthal angle of
arrival .PHI. can be calculated using the two diversity antenna
branches in accordance with Expression 1. In Expression 1, .PHI. is
the azimuthal angle of arrival; d.sub.antenna is the distance
between the two diversity antennas, and d.sub.arrive is the
projection of d.sub.antenna on the direction at which the signal
approaches the antenna (see FIG. 11). .PHI.=a
cos((d.sub.antenna)/(d.sub.arrive)) Expression 1
The action 13-3 above described essentially involves the rake
receiver 62 determining the delay difference measurement between
the two branches of a non-test user equipment unit (UE), which
delay difference is a skew or delay.sub.TOTAL for the non-test UE.
As understood from Expression 2, this skew or delay.sub.TOTAL
includes two components: (1) a first component (delay.sub.AOA)
which is contributed by the angle of arrival; (2) a second
component (delay.sub.HW) which is contributed by the hardware delay
difference between the two branches.
delay.sub.TOTAL=delay.sub.AOA+delay.sub.HW Expression 2
The second component of the skew, i.e., the component contributed
by the hardware delay difference between the two branches
(delay.sub.HW), was calculated at action 13-1 as the measurement on
a link which is set up by the test user equipment unit (UE) 30T
(which, it will be recalled, is positioned substantially
equidistantly in front of the two diversity antenna). Thus, in
accordance with Expression 2, as action 13-4 the delay.sub.HW
component (known from action 13-1) is subtracted from the total
skew (i.e., delay.sub.TOTAL) measured for a non-test user equipment
unit, to yield the delay difference due to the angle of arrival
(delay.sub.AOA) for the non-test user equipment unit.
Knowing the delay difference due to the angle of arrival
(delay.sub.AOA) after the calculation of action 13-4, as action
13-5 the parameter d.sub.arrive is calculated in accordance with
Expression 3. In Expression 3, "C" is the speed of light.
d.sub.arrive=delay.sub.AOA*C Expresison 3
At this point both d.sub.antenna and d.sub.arrive are known. The
parameter d.sub.antenna is known from simple length measurement at
the radio base station. The parameter d.sub.arrive is known from
the result of the calculation of action 13-5. With both
d.sub.antenna and d.sub.arrive known, as action 13-6 these values
are inserted in Expression 1, thereby enabling determination of the
azimuthal angle of arrival .PHI..
As action 13-8, the angle of approach determination unit 64-12
sorts the delay values due to angle of arrival (AOA) into one of
several delay value ranges, and then increments a counter
associated with the appropriate range. In so doing, a count of the
number of occurrence for each delay value range is maintained. Such
counts are stored as the number of occurrences in a matrix. FIG. 14
illustrates an example format of such a matrix for a multi-sector
(Change to cell/carrier) radio base station in which a receiver
board 60 serves the plural sectors (Change to cell/carriers). In
the matrix of FIG. 14, "D-10" represents the frequency (e.g.,
number) of samples where Branch B-Branch A equals -10 nanoseconds;
"D+10" represents the frequency (e.g., number) of samples where
Branch B-Branch A equals +10 nanoseconds; and so forth.
As action 13-9, a check is made whether all non-test user equipment
units (UE) in the sector using the specified cell/carrier that are
to be processed have been processed (e.g., that the non-test UE
loop has been executed for all non-test UEs). If the result of the
check of action 13-9 is negative, execution returns to action 13-2
for processing of a next non-test UE. Otherwise, as action 13-10
the stored values obtained during this session are transmitted to a
centralized data collection agent, e.g., main processor 70 in the
illustrated implementation. For the illustrated implementation, the
stored values can take the form of the very data matrix stored by
the angle of approach determination unit 64-12, e.g., the form of
FIG. 14, for example.
The actions of FIG. 13 can be performed at a frequency as required
by the service provider or network operator, e.g., at a pre-defined
frequency. In accordance with one implementation, the centralized
data collection agent, e.g., main processor 70, sums up the data
received in each report from the receiver board 60. For example,
main processor 70 can maintain a matrix much like that of FIG. 14
which stores cumulative values rather than session values. An
interface such as graphical user interface 80 connected to main
processor 70 can be used to display or output the cumulative
results in various forms. One example output or display form is
that of a histogram which can be utilized for cell planning
optimization.
Variations of the foregoing embodiments, including the third
embodiment, are within the scope of the present invention. For
example, as illustrated in FIG. 13, the processing of the non-test
UE loop normally occurs after action 13-1. However, the logic could
be alternatively configured so that the rake receiver measurements
for the non-test user equipment units (UE) are made at
substantially the same time as the measurements for the test user
equipment unit (UE) 30T, it being understood however, that
subsequent actions (e.g., actions 13-4 and following) require the
measurement of action 13-1 for completion.
The third embodiment thus allows a service provider to conduct
measurements on each radio base station and obtain a fairly
accurate estimate of the distribution of angle of arrival, and
thereby obtain an estimate of the traffic geographical
distribution. This analysis can then be used as input for
optimization of cell planning.
Whereas the embodiments previously described all pertain, at least
to some degree, to measuring an uplink delay difference between
branches of a sector having diversity antenna, the fourth
embodiment involves measuring downlink delay difference for a
cell/carrier for such a sector. One example mode of the fourth
embodiment is illustrated in FIG. 15. For each sector, the radio
base station 28 includes a sector transmit signal processing
section 140, which pertains to a cell/carrier and which connects to
the two diversity transmit antennas 144A and 144B for the
sector.
In similar fashion to the sector receive signal processing section,
the sector transmit signal processing section 140 processes two
branches of a radio link signal to be transmitted, and accordingly
has two branches 147A, 147B of signal processing hardware. The two
branches 147A, 147B of signal processing hardware respectively
process the two branches of the radio link signal received from on
lines 157A and 157B, respectively from a transmitter receiver board
160, also know as a TX board or TX. Each branch 147 of hardware has
an associated delay adjustment means (such as delay adjustment
buffer 155, shown as being located in the transit board 160, which
is where the RF and BB signals get converted to one another.
In addition, sector transmit signal processing section 140 includes
or interconnects to a processor, which can be (for example), the
main processor 70 of the radio base station previously described.
One function performed by such processor which is germane to an
embodiment of the present invention is delay alignment, as depicted
by closed loop downlink diversity branch delay alignment routine or
unit 172. The main processor 70 and the board processor 164
communicate with one another as depicted by processor communication
line 174.
In like manner with the receiver board 60 of previous embodiments,
the transmit board 160 can either be dedicated to a single sector,
or comprise a pool of boards wherein the 160 can be dedicated to a
single cell/carrier or to a single sector, or shared among plural
cell/carriers and/or sectors served by the radio base station.
FIG. 15 also shows that the user equipment unit (UE) 30T for the
fourth embodiment includes a transceiver 260 and a processor 270.
The processor 270 includes a rake receiver 262, which functions in
similar manner as the rake receiver 62 previously described but
with respect to diverse radio link signals received from differing
diversity antenna 44 of the same cell/carrier of the same sector of
the radio base station 28. In other words, the rake receiver 262 of
the test user equipment unit (UE) 30T measures a delay difference
between downlink radio signals of the cell/carrier received from
antennas 44A and 44B (see, e.g., FIG. 10).
FIG. 16 illustrates certain basic example steps and actions
performed in accordance with the fourth embodiment. These basic
steps are understood in the example context of FIG. 15. Upon
starting (depicted by symbol 16-1), the closed loop downlink
diversity branch delay alignment routine or unit 172 as action 16-2
sends a start signal to the test user equipment unit (UE) 30T. The
start signal of action 16-2 is transmitted as a special signal
using the transmit capabilities of the radio base station, in
similar manner as any other signal sent from the radio base station
28 to a user equipment unit (UE). In this regard, the test user
equipment unit (UE) 30T can be configured uniquely to recognize
this special start signal.
Upon receiving the start signal from the closed loop downlink
diversity branch delay alignment routine or unit 172, the rake
receiver 162 of the test user equipment unit (UE) 30T is authorized
to make delay difference measurements on the PDP pairs from two
diversity branches on each downlink radio link in the specified
measurement period. Such measurements of the delay difference are
performed as action 16-3 in FIG. 16. In actuality, in one
implementation, plural measurements are performed with respect to
each branch at a predetermined frequency, and the plural
measurements are averaged over the measurement period. Upon
expiration of the measurement period, using its transceiver 260 the
test user equipment unit (UE) 30T as action 16-4 sends a report of
the delay difference value to the closed loop downlink diversity
branch delay alignment routine or unit 172 at the radio base
station 28.
Upon receipt of the measurement report from the test user equipment
unit (UE) 30T, as action 16-5 the closed loop downlink diversity
branch delay alignment routine or unit 172 calculates a delay
adjustment value for the sector downlink signal processing section
140. The calculated delay adjustment value is then applied to an
appropriate one of the delay adjustment buffers 155.
It will be appreciated that the functions of various units and
processors described herein can be implemented in various ways,
including the functions of (for example) delay alignment unit 72,
cell planning unit 74, main processor 70, board processor 64; angle
of approach determination unit 64-12, processor 170, processor 270,
and closed loop downlink diversity branch delay alignment routine
or unit 172. For example, these functions may be implemented,
either individually or collectively, using individual hardware
circuits, using software functioning in conjunction with a suitably
programmed digital microprocessor or general purpose computer,
using an application specific integrated circuit (ASIC), and/or
using one or more digital signal processors (DSPs).
As appropriate given the diversity considerations, the embodiments
described above can be implemented in radio access networks of
types other than the UTRAN. For example, other types of
telecommunications systems which encompass radio access networks
include the following: Advance Mobile Phone Service (AMPS) system;
the Narrowband AMPS system (NAMPS); the Total Access Communications
System (TACS); the Personal Digital Cellular (PDS) system; the
United States Digital Cellular (USDC) system; and the code division
multiple access (CDMA) system described in EIA/TIA IS-95
While the invention has been described in connection with what is
presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not to be
limited to the disclosed embodiment, but on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
TABLE-US-00001 TABLE 1 For cell/carrier_ID = 1 to 6 If
(|TBranch_diff [cell/carrier_ID]| > TBranch_diff_Thresh) then If
(TBranch_diff [cell/carrier_ID] >= 0) then
TTRX_RF_UL[cell/carrier_ID,0] = TTRX_RF_UL[cell/ carrier_ID,0] +
TBranch_diff[cell/carrier_ID] Else If ( TBranch_diff
[cell/carrier_ID] < 0) then TTRX_RE_UL[cell/carrier_ID,1] =
TTRX_RF_UL[cell/ carrier_ID,1]- TBranch_diff[cell/carrier_ID] Endif
Send TTRX_RF_UL[cell/carrier_ID,0] and
TTRX_RF_UL[cell/carrier_ID,1] down to HW Endif Endfor
* * * * *